1. Field of the Invention
The present invention relates to a photosensitive material processor in which a photosensitive material of a photosensitive planographic printing plate and so forth is carried and is processed in a processing liquid.
2. Description of the Related Art
With respect to a photosensitive material, there is a photosensitive planographic printing plate (simply called as PS plate hereinafter) in which a photosensitive layer is formed on a support of aluminum and so forth. A PS-plate processor, which is a photosensitive material processing apparatus for processing the PS plate, performs a plurality of processes by using a processing liquid. As to these processes, for instance, there are a developing process in which the PS plate is dipped in a developer, a washing process in which water is applied onto the PS plate, and a desensitizing process in which a surface of the PS plate is coated with a desensitization treatment liquid of gum liquid and so forth after the washing process. In the PS processor, the processes of developing, washing, desensitizing and so forth are performed for the image-exposed PS plate.
In the developing process of this kind of the PS-plate processor, the PS plate is carried while dipped in the developer contained in a developing bath. By virtue of this, the photosensitive layer no longer required after the image exposure is removed from the surface of the PS plate. In the developer, ingredients of image colorant and so forth are transferred from the PS plate during the developing process of the PS plate. The transferred ingredients are deposited and aggregated to become solids. It is likely to cause a harmful effect that the solids adhere to the PS plate. If the developing process is finished in a state that the solids adhere to the PS plate, there arises a problem in that a print is soiled by the adhering solids. In consideration of this, filtration is performed by a filter so as to prevent the particulate ingredients, dust and so forth from adhering to the photosensitive material during the process (see Japanese Patent Laid-Open Publication Nos. 5-119454 and 2002-341504). Moreover, by projecting a delivery pipe of the processing liquid up to a predetermined height from the bottom of the processing bath, sediment deposited at the bottom of the processing bath is prevented from being raised up at a time of delivery of the processing liquid so that the sediment is prevented from adhering to the photosensitive material (see Japanese Patent Laid-Open Publication No. 2003-270766).
As mentioned above, when the processing liquid is continuously used, the liquid deteriorates and the solids generated due to the deterioration thereof causes the problem that the solids adhere to the photosensitive material. It is desired to improve this problem. For this purpose, factors for generating the solids in the developer have been keenly examined. As a result, the inventors of this application have found that the solids are generated due to a relationship between the developer and a heater used for keeping the developer at a constant temperature, such as described below. Some of the PS plates use water-insoluble image colorant, and a system is incorporated so as to prevent this image colorant from depositing and so as to maintain a dispersion state by employing binder ingredients. When processing this kind of the PS plate, the image colorant is transferred from the PS plate to the developer, and the binder ingredient included in the PS plate acts to maintain the dispersion state wherein the image colorant resides in the developer as if dissolving therein. When large amounts of the PS plates are processed, a density of the image-colorant ingredients increases. At this time, upon turning on the heater for stabilizing the temperature of the developer, the temperature of the developer rises at a heater surface. In a conventional heater drive, the heater is adapted to heat up a processing liquid at full power in order to make a waiting time shortest at the start of operation. The inventors of this application have found that the dispersion state of the image colorant breaks and the solids appear on the heater surface in a circumstance that a temperature of the heater surface is heated up so as to be about 80° C. or more. A part of the solids of the image colorant separates from the heater and adheres to the PS plate.
In consideration of this, it is necessary to set the temperature of the developer to a constant temperature or less near the heater surface for the purpose of preventing the occurrence of the solids. With respect to countermeasures for setting the temperature of the developer to the constant temperature or less near the heater surface, there are conceivable methods, in one of which an area of the heater surface is enlarged to lower watt density, and in another of which a circulating flow-velocity of the developer is increased at the heater surface. In these cases, there are problems in that the heater has a large size and a circulating pump of large capacity is necessary. Further, it is difficult to prevent the occurrence of the solid image-colorant gradients at a portion where the circulating flow hardly runs. Thus, these methods are not regarded as the ultimate countermeasures. It is also conceived to lower the watt density by reducing a capacity of the heater. In this case, however, there arises a new problem in that it takes a time to heat up the developer. At a start-up time of usual morning, this new problem may be solved by a timer standby function and so forth. Accordingly, troubles are not caused at the start-up time even if the heater has a small capacity. However, when preparing the new liquid, it is impossible to utilize the timer standby function. Thus, the heat-up time becomes long in a case that a temperature of running water is low at the time of preparation of the new liquid.